One router I don't see too many of out there, but which I think is great after owning one for almost a year, is the SMC Barricade series. Good external antennas give me almost twice the range (in a non-scientific test, that is, walking around with my iBook) compared to my old Airport 1 Base, and the http interface is nicely done. They're cheap, too.
I had to return the Linksys I bought originally as it didn't work well at all with my iBook. I might have just had a bad unit, though, as I hear a lot of people using them with macs. It ended up being good, though, since I like the SMC better anyway.
If you're just sharing internet access over the wireless, and won't be transferring many files between machines, there's no reason to sink the extra money into G since regular B is more than fast enough for that. As the previous poster said, though, it's nice to be future-proof.
Stay away from 802.11A- it's a dead standard now that G is out.